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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 6 |
| 2 | 27 |
| 3 | 98 |
| 4 | 315 |
| 5 | 918 |
| 6 | 2492 |
| 7 | 6367 |
| 8 | 15495 |
| 9 | 36145 |
| 10 | 81326 |
| 11 | 177219 |
| 12 | 375461 |
| 13 | 775544 |
| 14 | 1565870 |
| 15 | 3096615 |
| 16 | 6008917 |
| 17 | 11458720 |
| 18 | 21502964 |
| 19 | 39754385 |
| 20 | 72485518 |
| 21 | 130464603 |
| 22 | 231989748 |
| 23 | 407847488 |
| 24 | 709365160 |
| 25 | 1221364655 |
| 26 | 2082872680 |
| 27 | 3519963776 |
| 28 | 5897536697 |
| 29 | 9800358525 |
[1,6,27,98,315,918,2492,6367,15495,36145,81326, 177219,375461,775544,1565870,3096615,6008917, 11458720,21502964,39754385,72485518,130464603, 231989748,407847488,709365160,1221364655, 2082872680,3519963776,5897536697,9800358525] |